1. Field of the Invention
The present invention relates to methods for improving display quality of an image. More specifically, the present invention is directed to methods of performing cross color and/or cross luminance suppression to improve display quality.
2. Description of the Prior Art
In composite video television systems such as NTSC and PAL, a luminance signal and a chrominance signal share a portion of the available bandwidth. In NTSC, for example, chrominance information is encoded through a sub-carrier having frequency equaling 3.57955 MHz. Within the chrominance band extending from roughly 2.3 MHz to 4.2 MHz, the luminance spectrum overlaps that chrominance spectrum. This overlap results in signal interference.
It is well-known that a television decoder is implemented to extract both luminance information and chrominance information from the received composite signal; however, a typical simple television decoder cannot discern which of the higher frequency components are luminance information and which are chrominance information. As a result, such a television decoder generates incorrect chrominance information owing to the interference introduced via the luminance spectrum. The term “cross color” is commonly referred to as corruption of the chrominance spectrum caused by the misinterpretation of high-frequency luminance information as wanted chrominance information. Conversely, the term “cross luminance” is commonly referred to as corruption of the luminance spectrum caused by the misinterpretation of chrominance information as high-frequency luminance information.
Some conventional methods reduce cross color by operating upon chrominance information encoded on the chrominance subcarrier prior to demodulation into baseband chrominance information. These methods typically incorporate cross color suppression into the decoding process, focusing on improving the separation of the chrominance and luminance information to reduce both cross color and cross luminance.
However, cross color suppression is very desirable in applications where only demodulated baseband chrominance information is available, especially where demodulation was performed without much regard for suppressing cross color. In such applications, for practical reasons, cross color suppression must be performed in the baseband domain.
As such, Faroudja describes a technique for suppressing cross color in U.S. Pat. No. 5,305,120, the contents of which are hereby incorporated by reference. Although Faroudja suggests a feasible approach for post-decoding cross color suppression, a more optimized motion detection algorithm is desired in order to minimize possible error occurrence in the outcome of cross color suppression caused by over-simplified stationary image judgment.